1. Field of the Invention
The present invention relates to electrical systems for vehicles, and more particularly to a method and architecture for reduction of vehicle wiring through incorporation of modular power distribution panels providing primary and secondary distribution functions in a ring arrangement, and for implementation of point of use conversion devices to provide appropriate electrical power type and quality.
2. Description of the Related Art
A typical/conventional vehicle electrical distribution system is shown in FIG. 1. The electrical distribution system illustrated in FIG. 1 obtains power from various electrical power sources (10A, 10B, 20A, 20B, 50A and 50B) and distributes the power to various vehicle utilization systems and associated loads. Power supply systems 10A, 10B, 20A, 20B, 50A and 50B are exemplary generators, as illustrated in FIG. 1. Systems 10A, 10B, 20A, 20B, 50A and 50B may also be, or may include as needed, batteries, fuel cells and the like, to provide a primary electrical power source to an electrical distribution and conversion system. Vehicle utilization systems and loads include (but are not limited to) lights, valves, fans, pumps, actuators, and any other services required for performing utility functions on-board a vehicle during normal or abnormal operations.
FIG. 1 illustrates an existing typical/conventional electrical power system for vehicles. The electrical power system in FIG. 1 provides power generation, conversion and distribution functions. The electrical power system illustrated in FIG. 1 uses distribution panels (1100A, 1100B, 1200A, 1200B) for power network switching, load control and circuit protection. The panels are typically located at centralized positions within the vehicle. These distribution panels are generally categorized and segregated into distinct panels for primary power, high voltage (1100A and 1100B), primary power, low voltage (1200A and 1200B), secondary power distribution and protection (1300A and 1300B), and emergency power (1300C). The circuit breaker and emergency panels are located within reach of the crew, to allow for necessary crew interaction with the panels during vehicle operation. Most of the other panels are located in a common electrical bay, usually below or in the vicinity of the crew compartment. Distribution feeder cables 009A through 009F connect the power sources 10A, 10B, 20A, 20B, 50A and 50B to the centralized primary power distribution panels 1100A and 1100B in the electrical bay described above. The centralized primary power distribution panels 1100A and 1100B include, but are not limited to, electrical contactors, bus bars, relays, current and voltage monitoring and circuit protection devices, and electrical hardware arranged and connected for proper and safe distribution of bulk power provided by various power input sources 10A, 10B, 20A, 20B, 50A and 50B.
A certain amount of high voltage power may be used locally, for high power systems such as pumps, fans or actuators. This amount of high voltage power is supplied directly from the high voltage buses 1110 and 1120 in the primary power distribution panels 1100A and 1100B. Much of the high voltage power, however, is routed to conversion devices which transform high voltage and current to conventional voltages used by existing legacy equipment. Such legacy equipment includes various items of vehicle equipment previously designed for existing vehicles. Legacy equipment is reused because of industry availability and/or fleet logistics. Voltage conversion is typically performed by transformers, to obtain 115V AC power. Autotransformers (ATU) 1400A and 1400B are typically used for this purpose. Autotransformers use a common winding on the core without electrical isolation between primary and secondary stages. Hence, autotransformers have lower weight and are superior to classical transformers which have fully isolated primary and secondary windings. Transformer rectifier units (TRU) 1500A and 1500B combine both transformer and rectifiers within the same device, and are similarly used to obtain 28V DC from the high voltage primary power.
The transformed low voltage power is supplied to a second lower tier primary distribution panel (1200A, 1200B) via feeders 014A, 014B, 015A and 015B. The bulk power in these sub tier primary panels is subsequently subdivided into smaller portions (>50 Amperes) which are then routed to secondary power distribution panels (1300A, 1300B, 1300C) or directly to larger loads such as, but not limited to, fans, pumps, and heater loads from power buses 1210 and 1220. The sub tier primary power panels are close to the high voltage primary panels in the electrical bay, and, hence, form a centralized distribution system.
The 115V AC and 28V DC power routed to the secondary distribution panels (1300A, 1300B, 1300C) is further subdivided into individual utilization load levels (<30 Amperes) within the left and right secondary power distribution panels 1300A, 1300B and 1300C.
Due to the grouping of the primary distribution panels shown in FIG. 1, panels which are typically co-located in the electrical bay, the number of large diameter cables required to conduct high power from generators to various distribution panels is reduced in the “centralized” architecture of FIG. 1. However, smaller size wiring 018A, 018B, 018C, 019A, 019B, and 019C that connects central panel positions to aircraft wide utilization loads, and cables 016A, 016B, 016C, 016D, 017A, 017B, 017C and 017D that connect primary low voltage panels 1200A and 1200B to crew compartment mounted secondary and emergency power distribution panels 1300A, 1300B and 1300C, account for the bulk of the aircraft wiring weight. Large numbers of wires of smaller size are needed for a large number of single electrical loads that ultimately require a supply of power to function. For example, as many as 2000 single electrical loads can be present in a large commercial aircraft. While an individual small gauge wire does not present a significant weight, many such wires extending along great distances generate the most significant weight component for a particular vehicle system. Reducing the length of these wires can lead to significant weight reduction in a vehicle.
The traditional architecture illustrated in FIG. 1 was created to facilitate operator interaction with circuit protection devices while the vehicle is in operation. Additional benefits of such a centralized electrical bay installation were the consolidation of electrical equipment installations for manufacturing and maintenance tasks. To meet operator interface requirements, all secondary distribution had to be routed to the crew compartment location first. In aircraft applications, for example, a centralized electrical bay located below the flight deck provided a location for electrical hardware in proximity of flight deck interfaces.
Modern aircraft electrical power systems have moved away from the centralized architecture illustrated in FIG. 1. This development was spurred by the advent of remotely controlled switches and circuit protection devices that enabled the crew to monitor loads and change the status of circuit protection devices anywhere on the aircraft using digital network communications. In modern aircraft electrical power systems, individual load switches and protection are moved closer to the loads, using many smaller secondary distribution panels. These non-centralized secondary power distribution architectures bring weight and installation benefits, because they reduce the length of individual load small gauge wiring. Thus, non-centralized secondary power distribution architectures reduce the overall weight of secondary power wiring used for a vehicle wiring installation.
However, conventional centralized primary distribution panels are still used in the non-centralized secondary power distribution architectures. For this reason, cabling from the primary low voltage panels to remote secondary panels still account for a large wiring weight. Furthermore, these relatively large secondary feeders introduce new installation provision needs and routing problems, which diminish the benefits of modern aircraft electrical power distribution systems.
A modern typical/conventional non-centralized secondary power distribution architecture is generally represented in FIG. 2. The architecture in FIG. 2 is similar to the architecture in FIG. 1. However, in FIG. 2, the secondary power distribution and emergency panels, which were located in the crew compartment in FIG. 1, have been replaced by smaller remote distribution panels. An emergency power distribution panel has been omitted from the diagram of FIG. 2 to simplify the representation. Such a panel could be included in FIG. 2. However, in modern architectures, emergency functions are often consolidated into the remote systems, by providing a dedicated remote panel for emergency services, for example. One drawback of the non-centralized secondary power distribution architecture of FIG. 2 is the associated weight of power feeders (016A, 016B, 017A, 017B) that connect many secondary power distribution boxes (1300A, 1300B, 1300C, 1300D, 1300E, 1300F) to centralized primary power distribution equipment (panels 1200A and 1200B). The large number of power feeders connecting the centralized power distribution equipment to secondary power distribution boxes generates significant wiring weight. Also, the feeders connecting centralized power distribution equipment to secondary power distribution boxes have larger gauge, in order to reduce losses while distributing low voltage power over long distances within the vehicle, to supply low voltage power to distributed loads.
If the voltage level on a feeder cable is a conventional power voltage, such as 115 VAC or 28 VDC, the current in the feeder cable can be high for a given power transmission requirement. Consequently, feeder wire with large gauge is needed for the feeder cables, to carry large currents and minimize voltage drop over long distances. For reasons mentioned above, the feeder cables generate a significant weight in a typical/conventional vehicle distribution system. Hence, these feeder cables add significant weight in distributed secondary power architectures.
FIGS. 1 and 2 include, for completeness, double voltage (230V AC) power generation levels that are commonly permitted in contemporary vehicle designs. In some architectural configurations, vehicle designs may still incorporate 115V AC power generation, in order to eliminate the 230 VAC primary power panels (1110A, 1200A) and the ATUs (1400A, 1400B). Power panels 1200A and 1200B are typically split so that the power supply feeds 115V AC power into the primary AC panel, and the TRUs (1500A, 1500B) transform a portion of the 115V AC to 28V DC. The 28 V DC power may be further distributed by another such panel.
Current designs for aircraft electric power generation have moved to high voltage power outputs (230 VAC). High voltage power outputs enable lower current, high power generation, and facilitate dual use of the power generation source as a starter motor for the turbine engine on “More Electric” vehicles. Higher output voltage is useful for bulk power applications such as electrically driven pumps, fans and motor control electronic devices. However, higher output voltage is unsuitable for most general utility consumption applications, because existing utilization equipment available from current industry sources operates at lower voltage levels. Moreover, high output voltages that are generally distributed can cause human interaction safety concerns during direct operation and maintenance contact.
Therefore, high output voltage power obtained from a generator and passed into a primary power distribution panel, needs to be transformed to provide conventional power voltages, such as 115 VAC and 28 VDC for utilization equipment. This electrical power transformation is typically achieved through the use of large centralized power conversion equipment (ATUs 1400A and 1400B, TRUs 1500A and 1500B) located in the electrical bay next to the primary panels. Transformers 1400A and 1400B convert 230 VAC to 115 VAC. Similarly, transformer-rectifier units 1500A and 1500B use a 230V AC input, pass this power through a suitable step down winding, and further rectify the output to provide 28 VDC. A second primary distribution panel set 1200A and 1200B receives the converted power. The second primary distribution panel set performs power protection and distribution functions, and provides lower voltages to the distributed secondary power panels.
In the contemporary power distribution architecture described in FIG. 2, distributed secondary power boxes 1300A to 1300F are implemented like a conventional large individual load. For example, throughout the aircraft, distributed secondary power boxes are implemented with protection circuit breakers 1250A, 1250B and 1250C, along with cabling 016A, 016B, 017A, and 017B. Cabling 016A, 016B, 017A, and 017B connect the secondary distribution panels to the centralized power panel. However, cabling that connects the distributed secondary power boxes to the centralized power panel adds weight and complexity to the vehicle wiring. The added weight and complexity are related to the large gauge of cables. The large cable gauge is needed to satisfy installation requirements, and maintain voltage drop limits for higher current at a lower voltage level.
Disclosed embodiments of this application address these and other issues by utilizing an integral method and architecture for power distribution that reduces vehicle wiring in a system of distributed secondary power units, by using high voltage primary power and distributed low voltage conversion equipment. The architecture of the present invention extends the point-to-point generator output distribution to forward and aft electrical bays by implementing a ring distribution feeder approach. A high voltage ring is used to route power around the vehicle, hence providing bulk power to aircraft areas where electrical utility loads exist. Local conversion and secondary distribution of power are performed at appropriate locations along the primary power ring periphery. Such locations are identified by detailed study of a vehicle load locations and equipment location potential. Embodiments described in this application use a ring bus to distribute high voltage directly to an area of utilization serviced by secondary power distribution panels. Embodiments described in this application minimize wire gauge and reduce the length required for wires that distribute power to secondary power boxes. The ring architecture of the current invention uses forward and aft running “point to point” cabling, and makes full use of installed high voltage distribution cables, by completing a ring connection at specific locations. Appropriately sized local power conversion equipment items are placed adjacent to the secondary power distribution panels, and generate conventional power for local equipment. Embodiments described in this application eliminate dedicated feeders to secondary power distribution panels, offer alternative and more efficient power distribution solutions, and provide higher availability for electrical power distribution, through coordination of ring bus contactors and protection devices. Such coordination may be achieved with an expert supervisory control system with advanced control capabilities.